Designing an analog circuit requires attention to many nuances that are less relevant in digital circuit design. Unlike digital circuits, whose inputs/outputs are either on or off and have built in hysteresis to prevent inadvertent toggling, analog circuits are intentionally designed to respond to minor fluctuations in signal levels. As a result, analog integrated circuit designers, which include analog schematic designers and layout designers, are required to focus on semiconductor device physics such as gain, matching, power dissipation, and resistance.
Analog integrated circuits are also sensitive to process variations, which are further compounded with density requirements in small technology nodes such as 40 nm, 28 nm, and 16 nm. The process variations typically cause process mismatches and lead to an analog integrated circuit not performing as simulated. Layout designers follow physical layout requirements during the layout process to reduce the effects of the process variations of a given technology. Unfortunately, the physical layout requirements are not able to be modeled or simulated and, as such, the exact impact is unknown by an analog schematic designer. As a result, the analog schematic designer provides schematic information, notes, or verbal instructions to a layout designer who typically has to perform several layout iterations before meeting the physical layout requirements of a given target technology.